code: def testRFFT3D(self):
      def _to_expected(x):
          return np.fft.rfftn(
              x,
              axes=(-3, -2, -1),
              s=[x.shape[-3], x.shape[-2], x.shape[-1]],
          )
  
      def _tf_fn(x):
          return signal.rfft3d(
              x, fft_length=[x.shape[-3], x.shape[-2], x.shape[-1]]
          )
  
      self._VerifyFftMethod(
          INNER_DIMS_3D, np.real, _to_expected, _tf_fn, ATOL_3D, RTOL_3D
      )
  
imports: import itertools
  import numpy
  import scipy.signal
  from tensorflow.compiler.tests import xla_test
  from tensorflow.python.framework import dtypes
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import gradients_impl
  from tensorflow.python.ops.signal import signal
  from tensorflow.python.platform import googletest
label_desc: Use image node_id 11 for calling the FFTTest obj's underlying member method code with example usage: obj.testRFFT3D() and returns: np, signal